Photographic emulsions sensitized with oxonol dyes containing a 5(4)-thiazolone nucleus



Oct. 12, 1954 E. B. KNoTT "2,591,581

PHOTOGRAPHIC EMULsIoNs SENSITIZED WITH oxoNoL DYES CONTAINING A 5(4)-THIAZOLONE NUCLEUS Filed May 5, 1951 Fig- 1.

|| lr/flwlrllmml im 300 O 500 600 700mu B15 4 (2 BENZ YLrH/o -5 (4) rH/AzoLo/ve) MErH/NE oxo/VOL Fig. 2

Il MTH! lm ml IN |||1 Fig. 3

'l1 MTM Im m lll ml ml Edward Knofi INVENToR.

ATTE/MGT.

Patented Cet. 12, 1954 UNITED STATES A'I'EN'Iv OFFICE PHOTOGRAPHIC EMULSIONS SENSETIZED WITH OXIONL DYES CONTAINING A 5 4) -THIAZQLNE NUCLEUS Edward B. Knott, V/ealdstone, England, assigner to Eastman Kodak Company, Rochester, N. Y., a, corporation of New llersey application May 5,1951, sel-isi Ne. 224,714

(ci. asm?) 16 Claims. l

This invention relates to photographic silver halide emulsions containing sensitizing dyes and to certain new sensitizing dyes.

Certain dyes of the cyanine and merocyanine classes are known to alter the sensitivity of pho` tographic emulsions. Dyes of the oxonol class have also been used for this purpose, but, in general, these dyes have been found to be extremely weak sensitizers. Now I have found that oxonol dyes containing a 2alkylthio5(4) -thiozolone nucleus can advantageously be used to sensitize photographic silver halide emulsions. Some of the dyes of my invention possess sensitzing power approaching that of the merocyanine dyes, which was quite surprising in View of the known deficiencies of oxonol dyes previously employed for this purpose.

An object of my invention is to provide photographic silver halide emulsions sensitized with oxonol dyes. Another object is to provide a sup-- port coated with such sensitized emulsions. Still another object is to provide certain new oxonol dyes. A further object is to provide methods for obtaining these new dyes. Other objects will become apparent from a consideration `of the following description and examples.

The oxonol dyes useful in practicing my invention can be represented by the following general formula:

wherein R represents an alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-amyl, n-hexyl, Z-ethylbutyl, n-heptyl,

heterocyclic ring, such as those selected from the group consisting of a thiozolone nucleus, lfor example, a 2,4(3,5)thiazoledione nucleus, such as 2,4(3,5)thiazoledione, 3ethyl-2,4(3,5)thi azoledione, 3phenyl-2,4(3,5) -thiazoledione or 3naphthyl-2,4(3,5)-thiazoledione nuclei, a 2- thio-2,4(3,5)-thiazoledione (a rhodanine) nudione (3-alkylrhodanine), 3-phenyl-2-thio- 2,4(3,5) -thiazoledione (S-phenylrhodanine) 3- naphthyl-2-thio-2,4(3,5) -thiazoledione (S-naphthylrhodanine) nuclei or 3-(1-benZothiaZyD-2- thio2,4(3,5)thiazoledione (B-(l benzothiaZy1-) rhodanine) nuclei, a 2-thio-2,5(3,4)-thiazoledione nucleus, such asl 3-methyl2-thio-2,5(3,4) thiazoledione, 3-ethyl-2-thio-2,5(3,4) thiazoledione, 3-n-hepthyl-2,5(3,4) -thiazoledione, S-CycloheXyl-2,5(3,4)-thiazoledione, etc., a 2a1l yl mercapto-4(5)thiazolone nucleus, such as 2- ethylmercapto-l( 5) -thiazolona a 5(4)-thiazolone nucleus, such as a 2-alkylmercapto-5(4) thiazolone nucleus, for example, 2-ethylmercap 'to-5(4)thiazolone, 2-n hexylmercapto 5(4)- thiazolone, 2-noctylmercapto-5(4) thiazolone, 2ndecylmercapto5(4) thiazolone, 2 n dedecylmercapto-5 (Il) -thiazolone, 2-n-tetradecy1- mercapto5(4) thiazolone, 2 n hexadecylmerthiazolone nucleus, for example, 2-acetamino- 5(4) -thiazolone, Z-n-butyramino 5(4) thiazolone, 2-benzamino5(4)-thiazolona etc., a 2al koxy5(4)thiazolone, for example, 2-n-tetradecoxy-5(4)thiazolone, etc., a thiazolidone nucleus, such as 4-thiazolidone or its -alkyl, 3- phenyl or 3-naphthyl derivatives, a 2-alkylpheny1amino4(5)thiazolone nucleus, or a Z-dipheny1amino4(5)thiazolone nucleus; an oxazolone nucleus, for example, a 5(4)-oxazolone nucleus (e. g. 2-phenyl-5(4)oxazolone, etc.) a 2thio 2,4(3,5)oxazoledione nucleus, such as a 3-alkyl- 2-thio2,4(3,5) -oxazoledione nucleus; an imidazolone nucleus, for example a 2,4(3,5)imidazo1e dione nucleus, such as 2,4(3,5)imidazoledione (hydrantoin) or its S-alkyl, 3-phenyl or Sfnaphthyl derivatives as well as its 1,3-dialkyl, l-alkyl- 3-pheny1, 1alkyl3naphthyL 1,3-diphenyl, etc., derivatives, a 2thio-2,4(3,5)-imidazoledione nucleus, such as 2thio2,4(3,5)-imidazoledione (2- thiohydantoin) or its 3'alkyl, 3-phenyl or 3-naph thyl derivatives as well as its 1,3-dialkyl, 1-alkyl B-phenyl, l-alkylS-naphthyl, 1,3-diphenyl, etc., derivatives, a 2-alkylmercapto-5(4) -imidazolone such as 2propylmercapto-5 4 -imidazolone a thionaphthenone nucleus, such as 2(1)-thionaphthenone or 1(2) -t'hionaphthenona a pyraZ- clone nucleus, an oxindole nucleus, such as 2,3- dihydro-S-ketoindole, and like ve-membered heterocyclic nuclei, a 2,4,6-triketohexahydropyrimidine nucleus, for example barbituric acid or'2-thiobarbituric acid, as well as their l-alkyl or 1,3-dialkyl derivatives; a 3,4=-dihydro-2(1) quinolone nucleus, such as 3,4-dihydro2(l) quinolone (dihydrocarbostyril) a 3,4-dihydro- 2(1)-quinoxalone nucleus, such as :3A-dihydro- 2(1)-quinoxalone (oxydihydroquinoxaline) 3- phenomorpholone (1,4.,2-benzoXaZine-3(4) -one or benzo--morpholone) nuclei; 1,4,2-benzothiazine-3 (4) -one (keto-dihydrobenzoparathiazine) nuclei, and the like siX-membered heterocyclic nuclei. The dyes wherein Q represents the nonmetallic atoms necessary to complete a heterocyclic nucleus containing ve atoms in the heterocyclic ring, three of said atoms being carbon atoms, one of said atoms being a nitrogen atom, and the other of said atoms being a sulfur atom, a nitrogen atom, or an oxygen atom, have been found to be especially well adapted to the manufacture of photographic emulsions, I have found.

It has been further found that oxonol dyes selected. from those represented by Formula I wherein Q represents the nonmetallic atoms necessary to complete a 2-alkylthio-5(4) -thiazolone nucleus, the alkyl group of which is-a long-chain alkyl group, are especially useful in practicing our invention. Such oxonol dyes embraced by Formula I can be represented by the following wherein R has the values set forth above, and fR-i represents an alkyl group, especially a longchain alkyl group, such as n-hexyl, n-heptyl, n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, stearyl, n-eicosanyl, etc. (especially an alkyl group of the formula C11H2n+1 wherein 11. represents a positive integer from 6 to 20.

The oxonol dyes represented by Formula I above can advantageously be prepa-red by condensing a 2-alkylthio-5(4)-thiazolone selected from those represented by the following general wherein R has the values set forth above, with a 4-ethoxymethylene compound selected from those represented by the following general formula:

wherein Q has the values set forth above and R2 represents a hydrogen atom or an alkyl group, such as methyl, ethyl, etc.

The condensations can advantageously be carried out in the presence of a basic condensing agent, such as the trialkylamines (e. g. triethylamine, tri-n-propylamine, triisopropylamine, trin-butylamine, triisobutylamine, tri-n-amylamine, etc.), N,Ndialky1anilines (e. g. N,N-dimethylaniline, N,N-diethylaniline, etc), heterocyclic tertiary amines (e. g. N-alkylpiperidines, such as N-methylpiperidine, N -ethy1piperidine, etc., pyridine, quinoline, etc.) etc. Inert solvents can also be employed, if desired. Typical inert solvents include the aliphatic alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, etc., diethyl ether, chloroform, carbontetrachloride, benzene, toluene, Xylenes, n-pentane, n-hexane, n-heptane, 1,4-dioxane, acetone, glycol, etc. Heat accelerates the condensations, and temperatures varying from room temperature (about 25 C.) to the reflux temperature of the reaction mixture can be employed.

The intermediates represented by Formula III above can advantageously be prepared by refiuxing an ester selected from those represented by the following general formula:

v. s o

wherein R has the values set forth above with acetic anhydride. The intermediates represented by Formula V can advantageously be prepared by intermixing an aqueous alkali metal hydroxide solution, carbon disulfide, and glycine, lfollowed by addition kof an alkyl halide to the alkali metal salt (M-s--NH-CHT-(HJ-OM) formed, heating the mixture at a temperature of from about 40 to V100 C., and acidifying the reaction mixture to give the desired ester represented by Formula V above. These steps can be illustrated by the following general equations:

[BH-acid R.-S- LJ-NH-CH2 UJ0H wherein M represents an alkali metal and X2 represents a halogen atom, This method has been previously described by C'ook, Harris, Heilbron, and Shaw-"Jour: Chem. Soc. (London) 1948. pp. 1056-1060.

The intermediates represented by Formula IV above can advantagouesly be prepared according to the methods described by Cook et al.-Jour. Chem. Soc.-(1949), pp. 1435-7, and in "The Chemistry of Penicillin, Princeton Univ. Press (1949) p. 803. Other methods of preparing these intermediates have been described in the copending application Serial No. 211.566,.'led on February 17, 1951, in the names of Per Aubert and Edward B. Knott.

Alternatively, the oxonol dyes represented by Formula I above can be prepared by condensing a vketomethylene compound selected from those represented by the following general formula:

VI. /Q\` H26 =O wherein Q has the values set forth above, with a 4-ethoxymethylene compound selected from those represented by the following general formula:

VII.

wherein R and Rz have the values set forth above.

These condensations can advantageously be carried out in the presence of a basic condensing agent, such as the trialkylamines (e. g. triethylamine, tri-n-propylamine, triisopropylamine, trin-butylamine, triisobutylamine, tr-n-amylamine, etc.) N,N-dialkylanilines (e. g. N,Ndi methylaniline, N,Ndiethylaniline, etc), N-alkylpiperidines (e. g. N-methylpiperidine, N-ethylpiperidine, etc.), heterocyclic tertiary amines (e. g. pyridine, quinoline, isoquinoline, eta), etc. The condensations can advantageously be carried out in the presence of an inert diluent, such as the aliphatic alcohols (e. g. methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, etc.) diethyl ether, 1,4-dioxane, chloroform, carbontetrachlcride, benzene, toluene, xylenes, n-pentane, n-hexane, n-heptane, etc. Heat accelerates the condensations and temperatures varying from room temperature (about 25 C.) to the reflux temperature of the reaction mixture.

The intermediates represented by Formula VI above are, in general, well known substances. Intermediates of Formula VII above can be prepared according to the method described in application Serial No. 211,566 mentioned above.

The following examples will serve to illustrate more fully the manner whereby I practice my invention.

Example 1 .-Bz's-4- (Z-ethylthio- (4) -thz'azolon methineoxonol Is-*'i--on (llis C2H5s-c C-CH=C J-s-Cm N This dye was prepared according to the method of Cook et al. (loc. cit). It sensitized a gelatino silver chloride emulsion with a maximum at 520 m/L and a gelatine silver bromiodide emulsion with a maximum at 540 ma.

This dye was prepared according to the method of Cook et al. (loc. cit.). It sensitized a gelatine silver chloride emulsion with a maximum at 540 ma and a gelatine silver bromiodide emulsion with a maximum at 545 ma.

1.1 g. of 2-benzylthio-5(4) -thiazolone (Cook et al., Jour. Chem. Soc, 1948, p. 1056) and 1.1 g. of 4ethoxymethylene2-pheny1 5 (4) oxazolone (The Chemistry of Penicillin, Loc. cit.), cc. of ethanol, and 1.0 cc. of triethylamine were heated together on a steam bath for three minutes, diluted with Water, and the mixture then made acid. The resulting red oil was chilled, whereupon it solidied. It was recrystallized from acetone as soft, colorless needles melting at 136 C. Its solutions in organic solvents were orange-colored, while its aqueous alkali solutions were yellow. It sensitized a gelatino silver chloride emulsion with a maximum at 520 mp. and a gelatino silver bromiodide emulsion with a maximum at 540 ma.

i 1.8 g. of N-dithiocarbethoxyglycine and 10 cc.

6 of acetic anhydride were heated together for 30 minutes at C. and the volatile liquids removed under a vacuum.

3.31 g. of N-dithiocarbo-n-tetradecoxyglycine, 15 cc. of acetic anhydride, and 7 cc. of ethyl orthoformate were heated for 30 minutes at 130 C., and the volatile liquids removed under a vacuum. The 2-ethylthio5(4)-thiazolone obtained above was then added along with 10 cc. of ethanol and 2 cc. of triethylamine. The whole was heated on a steam bath for 5 minutes, cooled, diluted with 50 cc. of water, and made acid with dilute hydrochloric acid. The resulting oil solidiiied on standing to give 4.2 g. of crude product. It was recrystallized from acetone as orangebrown needles melting at 74 C. It sensitized a gelatino silver chloride emulsion with a maximum at 525 m/i and a gelatine silver bromiodide emulsion with a maximum at 535 ma.

1.8 g. of N-dithiocarbethoxyglycine and 10 cc. of acetic anhydride were heated together for 30 minutes at 120 C., and the volatile liquids removed under a vacuum.

2.6 g. of N-dithiocarbo-n-octoxyglycine, 15 cc. of acetic anhydride, and 5 cc. of ethyl orthoformate were heated at 120 C'. for 30 minutes, and the volatile liquids removed under a vacuum. The 2-ethylthio5(4) -thiazolone obtained above was then added along with 10 cc. of ethanol andv 2 cc. of triethylamine. The whole was then heated on a steam bath for 5 minutes, cooled, diluted with 50 cc. of Water, and made acid with dilute hydrochloric acid. The resulting oil solidied on triturating with acetone. It was recrystallized from acetone as violet needles melting at 76 C. 1t sensitized a gelatino silver chloride emulsion with a maximum at 520 ma and a gelatino silver bromiodide emulsion with a maximum at 535 ma.

Example 7.-[4- rz-n-ocryahio-s) amazozone) i [4- (2-phen'yZ-5 (4) -oxaeolofnw methz'neoaonol 1.1 g. of' -etlioxymethylene-2-phenyl-5-(4) oxazolone, 2-n'octylthio 5(4)- thiazolone- (obtained by heating together' 1.35 g. of NT-dithiocarboenf-octoxy'glycine' and 101Go. of acetic anhydride according to' the method' described in Example above), 10 cc. oi ethanol, and 1 cc. of triethyl'amine were heated together on a steam bath for 3 minutes. The reaction mixture was then diluted with water, and made acid with dilute hydrochloric acid. The' red oil which precipitated solidified on standing overnight. It was recrystallized from acetone as iiuiy, pink needles melting at 168 C. It sensitized a gelatino silver chloride emulsion with a maximum at 520 my.

2-n-octythio5(4)-thiazolone (obtained by heating together 1.3 g. of Ndthiocarbo-n.oc toxyglycine and cc. of acetic anhydride according to the method described in Example 5 above, 1.2 g. of 2-acetamino5(4) -thiazolone obtained as described in the copending application Serial No. 203,525, filed on December 29, 1950, in the names of Per Aubert and Edward B. Knott), 10 cc. of ethanol, and 3 cc. of triethylamine were heated together for 5 minutes on a boiling water bath. The solution was chilled, acidied with dilute hydrochloric acid, and the sticky crystals which precipitated recrystallized from acetic acid as a brown crystalline powder melting at 228 C. It sensitized a gelatino silver chloride emulsion with a maximum at 520 mp and a gelatino silver bromodide emulsion with a maximum at 530 In a like manner, by replacing the 4-ethoxymethylene-2phenyl-5(4)-oxazolone used in Example 7 by a molecularly equivalent amount of 4-(1ethoxyethyiidene) 2 ethylthio-5(4) ,-thiazolone, i. e.

O H3C --S csiro-d'1 (Lacan (obtained according to application Serial No. 211,566 sup-ra), [4-(2-ethylthio-5(4) -thiazolone) l {4-(2-11-octyl-thio 51(4) thiaz0lone)l methylmethineoxonol represented by the following formula:

can be obtained.

The N-thiocarbo-n-tetradecoxyglycine employed in Example 4 was prepared as follows:

Example 9.-N-thocarbo-n-tetradecomyglycine i HotlJ-oHg-NH-h-o-oHz-(cnme-cm 1 g. mol of tetradecanol was dissolved in 250 cc. of carbondisuliide and 1 g. mol of finely powdered potassium hydroxide added. The Whole was then shaken mechanically until it had set to a solid. After chilling overnight, the salt was collected,

washed with 'diethyi ether, and air-dried to give the desired potassium n-tetradecyl Xanthate.

This product obtained. above was added to 2250v cc. o' methanol and 1 g. mol. of ethylv bromide added. The reaction mixture was then warmed for several minutes, anddiluted with Water. The aqueous layer was separated and the oil remaining was taken up in diethyl ether. The ether layer was dried over sodium sulfate, and the ether removed. The ethyl n-tetradecoxy xanthate thus formed was used directly in the next step.

1 g. mol. of the ethyl n-tetradecyl xanthate formed above, 1 g. mol. of glycine, and 1 g. mol. of potassium hydroxide dissolved in a mixture 100 cc. of water and cc. of ethanol were heated under reflux on a steam bath for 1S hours. The reaction mixture was concentrated to 100 cc., and 100 cc. of water was added. The solution was made acid with concentrated hydrochloric acid. The solid which separated was recrystallized from petroleum ether as fine needles melting at 67 C.

By replacing the n-tetradecanol used in Example 9 by molecularly equivalent amounts of other alcohols, the following intermediates useful in practicing my invention were prepared:

Ethyl colorless needles 179-186 Water.

isopropyl long, at needles- 129 Do. n-Butyl. glossy needles- 70-71 Do. n-AmyL- needles 49-50 petroleum ether. t-Amyl hair-like needles.. 52-54 D0. n-Hexyl small needles 62 Do. n-Hcptyl o 66 Do.

n-Octyl fine needles 72 Do. n-Decyl glistening p1ates 63 Do. n-Dodecyl une needles 67 Do. n-Hexadecyl do 77 Do. ^ll?henyl-propyl. asbestos-like nee- 88 benzenep e tr o dles. leum ether.

The N-dithiom-octoxyglycine used in Example 5 was prepared as follows:

Example 10.-N-dithiocarbo-n-octomyglycine 22.4 g. of potassium hydroxide were dissolved in 50 cc. of Water and the solution chilled. There were then added 15.0 g. of glycine and 15.2 g. of carbondisulfide, and the Whole shaken mechanically until a clear orange solution resulted. A solution of 38.6 g. of n-octylbromide in 50 cc. of ethanol was added, and the mixture heated for 30 minutes on a steam bath. To the resulting one-phase solution there were added 100 cc. of water, and the cloudiness resulting removed by extraction with diethyl ether. The aqueous layer was warmed gently under reduced pressure to expel any dissolved ether, the solution chilled, and acidied with concentrated hydrochloric acid. The precipitate was collected on a filter, washed with Water, air-dried, and recrystallized from petroleum ether (bp. 60-80 C.) as glistening plates melting at 100 C.

By replacing the n-octyl bromide used in Example 10 by a molecularly equivalent amount of n-dodecyl halide, the N-dithiocarbo-n-dodecoxyglycine used in Example 6 was obtained as glossy plates melting at 111 C. on recrystallization from ligroin.

To prepare photographic emulsions sensitized with my dyes, it is only necessary to disperse the dyes in the emulsions. It is convenient to add the dyes to the emulsions from solutions in appropriate solvents. Methyl alcoholhas proven satisfactory for this purpose. Ethyl alcohol can also be used. Sensitization by means of these dyes is, of course, directed primarily to the ordinarily employed gelatino-silver-halide developing-out emulsions. The dyes (one or more) are ordinarily incorporated in the washed, iinished emulsions and should, of course, be uniformly distributed throughtout the emulsion. The concentration of the dyes in the emulsions can vary widely, i. e. from about to about 100 mg. per liter of owable emulsion. The concentration of the dye will vary according to the type of light-sensitive material in the emulsion and according to the eiect desired. The suitable and most economical concentration for any given emulsion will be apparent to those skilled in the art of emulsion making. To prepare a gelatinosilver-halide emulsion sensitized with one more of these dyes, the following procedure is satisfactory. A quantity of the dye is dissolved in methyl alcohol or other suitable solvent, and a volume of this solution (which may be diluted with water) containing from 5 to 100 mg. of dye is slowly added to 1000 cc. of gelatino-silverhalide emulsion, with stirring. stirring is continued until the dye is uniformly distributed throughout the emulsion. With most of these sensitizing dyes, to 20 mg. of dye per liter of emulsion sufces to produce the maximum sensitizing effect with the ordinary gelatine-silverbromide (including bromiodide) emulsions. With gelatino-silver-chloride emulsions somewhat larger concentrations may be required to produce the optimum sensitizing efect. The above statements are only illustrative and are not to be understood as limiting my invention, as it will be apparent that these dyes can be incorporated by other methods in photographic silver halide emulsions customarily employed in the art. For instance, the dyes may be incorporated by bathing a plate or nlm upon which an emulsion has been coated in a solution of the dye in an appropriate solvent. Bathing methods, however, are not to be preferred ordinarily.

The accompanying drawing further illustrates my invention. Each figure is a diagrammatic reproduction of a spectrogram showing the sensitivity of an ordinary gelatino-silver-bromiodide emulsion containing one of my sensitizing dyes. In Fig. 1, the curve depicts the sensitivity of an ordinary gelatino silver-brorniodide emulsion containing bis-4- (2-benzylthio-5 (4) thiazolone) methineoxonol. In Fig. 2, the curve depicts the sensitivity of an ordinary gelatino-silver-bromiodide emulsion containing [4-(2-benzylthio- 5(4) thiazolone) l [4 (2 phenyl 5(4) oxazclone) l-methineoxonol. In Fig. 3, the curve depicts the sensitivity of an ordinary gelatinosilver-bromiodide emulsion containing [4-(2- ethylthio 5(4) thiazolone) l [4 (2 n octylthio 5(4) -thiazolone)l methineoxonol,

Emulsions sensatized with my thiazolone dyes can be coated on the usual supports of paper, cellulose acetate nlm, glass, polyvinyl acetal resin nlm, metal, etc., in the usual manner.

What I claim as my invention and desire secured by Letters Patent of the United States is:

l. A photographic silver halide emulsion sensitized with at least one oxonol dye selected from those represented by the following general formula:

wherein R represents an alkyl group and Q represents the non-metallic atoms necessary to complete a heterocyclic nucleus containing five atoms in the heterocyclic ring, three of said atoms being carbon atoms, one of said atoms being a nitrogen atom, and the other of said atoms being selected from the group consisting of a nitrogen atom, an y'oxygen atom, and a sulfur atom.

3. A photographic silver halide emulsion sensitized with at least one oXonol dye selected from those represented by the following general formula:

rrr@ R-s-o o-on=' `c=o wherein R represents an alkyl group and Q represents the non-metallic atoms necessary to cornplete a heterocyclic nucleous of the 2acylamino 5 (4) -thiazolone series.

4. A photographic silver halide emulsion sensitized with at least one oxonol dye selected from those represented by the following general formula:

wherein R represents an alkyl group and Q represents the non-metallic atoms necessary to complete a heterocyclic nucleous of the 5(4) -oxazolone series.

5. A photographic silver halide emulsion sxensitized with at least one oxonol dye selected from those represented by the following general formula:

wherein R and R1 each represents an alkylL group.

6. A photographic silver halide emulsion sensitized with at least one oxonol dye selected from those represented by the following general formula:

sc-OH wherein R represents an alkyl group of the formula CmI-Izmifi wherein m represents a positive integer from l to 20, and Q represents the nonmetallic atoms necessary to complete a heterocyclic nucleus of the 2acylamino-5(4) thiazolone series.

7. A photographic silver halide emulsion sensitized with at least one oxcnol dye selected from those represented by the following general formula:

wherein R represents an alkyl group of the formula CMI-12min wherein m represents a positive integer from 1 to 20 and Q represents the nonmetallic atoms necessary to complete a heterocyclic nucleus of the 5(4)-0Xaaolone series.

8. A photographic silver halide emulsion sensitized with at least one oxonol dye selected from those represented by the following general formula:

`wherein R and R1 each represents an alkyl group vvof the formula Cmll2m+1 wherein m represents a positive integer from l to 20.

9. A photographic silver halide emulsion sensitized with at least one oxonol dye selected from those represented by the following general formula:

R-S-t t-Csz (LH, N n lwherein R represents an alkyl group of the formula CmHzmH wherein m represents a positive integer from 1 to 20 and R1 represents an alkyl group of Athe `formula CnHznH wherein n represents a positive'integer from 6 to 20.

10. A photographic silver chloride emulsion sensitized with at least one oxonol dye selected from those represented by the following general formula:

wherein R represents an alkyl group and Q represents the non-metallic atoms necessary to complete a heterocyclic nucleus containing five atoms in the heterocyclic ring, three of said atoms being carbon atoms, one of said atoms being a nitrogen atom, and the other of said atoms being selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom.

1l. A photographic silver bromiodide emulsion sensitized with at least one oxonol dye selected from those represented by the following general formula:

wherein R represents an alkyl group and Q represents the non-metallic atoms necessary to complete a heterooyclic nucleus containing five atoms in the heterocyclic ring, three of said atoms being carbon atoms, one of said atoms being a nitrogen atom, and the other of said atoms being selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom.

l2. A photographic silver halide emulsion sensitized with the, oxonol 'dye having the following formula:

13. VA photographic silver khalide lemulsion sensitized with the `oxonol dye vhaving :the following formula:

14. A photographic silver halide emulsion sensitized with the oxonol dye having the following formula:

l5. A photographic silver halide emulsionsensitized with the oxonol dye having the following formula:

16. A photographic silver halide emulsion sensitized with the oxonol dye having .the following formula:

References Cited in the le of this patent UNITED STATES PATENTS Chemical Abstracts 19:53() (Abstract'of Proc. Roy Soc., London, 96B 317-333,'1924). 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION SENSITIZED WITH AT LEAST ONE OXONOL DYE SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 